Recently, spatial search technology in a sensor network environment where a sensor network database and a spatial information database are converged has been actively researched.
The spatial search technology in the sensor network environment is used for searching for user-desired sensor nodes by using a spatial area in the case of searching for the user-desired sensor nodes from a plurality of sensor nodes in the sensor network. Such a spatial search technology has a merit of promptly searching for the user-desired sensor nodes while minimizing power consumption of sensor nodes when all the sensor nodes know their location information (x, y) and a user wants to search for sensor nodes contained in specific spatial areas (x1, y1, x2, and y2).
A distributed spatial index (DSI) method that is shown in FIG. 1 and FIG. 2 is a conventionally representative spatial search technology in a sensor network environment.
FIG. 1 and FIG. 2 are block diagrams of a conventional DSI method in a sensor network environment.
As shown in FIG. 1 and FIG. 2, according to the conventional distributed spatial search method in the sensor network environment, each node stores identifiers (IDs) of its child nodes and a minimum bounding rectangle (MBR) that contains all child nodes. Therefore, when a search area R is given as shown in FIG. 1, the sink node 0 10 compares MBRs A, B, and C of its child nodes 1, 2, and 3 (20, 40, and 30 of FIG. 1) with the search area R before transmitting messages to the child nodes 1 20, 2 40, and 3 30 and the search area R is transmitted only to the child node 3 30 that has an intersection with the R. Such a distributed spatial search method has a merit of reducing power consumption of sensor nodes in visiting its child nodes by filtering out the child node 1 (20) and the child node 2 40 in advance.
The conventional distributed spatial index method can be efficiently used for spatial searching for sensor nodes in a signal sensor network, but, in a heterogeneous sensor networks environment where more than two different sensor networks exist, it cannot provide an answer for a spatial join query that inquires a spatial relationship related to a location between sensor nodes, each of which is included in a different sensor network.